An internal constitution, firmly established on the principles of right, would not only serve to kill the seeds of national hatred and diminish the likelihood of foreign war. It would do more: it would destroy sources of revolution and discontent within the state. Kant, like many writers on this subject, does not directly allude to civil war[73] and the means by which it may be prevented or abolished. Actually to achieve this would be impossible: it is beyond the power of either arbitration or disarmament. But in a representative government and the liberty of a people lie the greatest safeguards against internal discontent. Civil peace and international peace must to a certain extent go hand in hand. [73] St. Pierre actually thought that his federation would prevent civil war. See _Project_ (1714), p. 16. We come now to the central idea of the treatise: (_c_) the law of nations must be based upon a federation of free states. (Art. 2.)[74] This must be regarded as the end to which mankind is advancing. The problem here is not out of many nations to make one. This would be perhaps the surest way to attain peace, but it is scarcely practicable, and, in certain forms, it is undesirable. Kant is inclined to approve of the separation of nations by language and religion, by historical and social tradition and physical boundaries: nature seems to condemn the idea of a universal monarchy.[75] The only footing on which a thorough-going, indubitable system of international law is in practice possible is that of the society of nations: not the world-republic[76] the Greeks dreamt of, but a federation of states. Such a union in the interests of perpetual peace between nations would be the “highest political good.” The relation of the federated states to one another and to the whole would be fixed by cosmopolitan law: the link of self-interest which would bind them would again be the spirit of commerce. [74] See p. 128. [75] This was the ideal of Dante. Cf. _De Monarchia_, Bk. I. 54:—“We shall not find at any time except under the divine monarch Augustus, when a perfect monarchy existed, that the world was everywhere quiet.” Bluntschli (_Theory of the State_, I. Ch. ii., p. 26 _seq._) gives an admirable account of the different attempts made to realise a universal empire in the past—the Empire of Alexander the Great, based upon a plan of uniting the races of east and west; the Roman Empire which sought vainly to stamp its national character upon mankind; the Frankish Monarchy; the Holy Roman Empire which fell to pieces through the want of a central power strong enough to overcome the tendency to separation and nationalisation; and finally the attempt of Napoleon I., whose mistake was the same as that which wrecked the Roman Empire—a neglect of the strength of foreign national sentiment.